JF Ptak Science Books   Quick Post   History of Lines 

These are particularly fine and relatively early printed images depicting a specific kind of line of sight–this one, a positioning, rather than a line of sight in fire control, or radial velocity, EM radiation or acoustics wave propagation, or targeting…this instrument was used to establish an imaginary line in perceived objects. 

This is a detail from Andrew Wakley’s  The mariner’s compass rectified : containing tables, shewing the true hour of the day, the sun being upon any point of the compass ; with the true time of the rising and setting of the sun and stars, and the points of the compass upon which they rise and set … With the description and use of those instruments most in use in the art of navigation. Also a table of the latitudes and longitudes of places, published in 1763 and reprinted many times after that. (Full text is available from Google books and also from the Haithi Trust which offers a text version of the book as well.)